What should I use instead of copy?

[alanhoff]

The caveats mention that one should not use copy since it can easily blow up the stack size. What's the recommended method for passing bytes from one stream into another?

[Xudong-Huang]

we can impl a copy fn simply like this

fn copy<R: Read, W: Write>(from: &mut R, to: &mut W) -> io::Result<u64> {
    use std::io::ErrorKind;
    // use buf from heap instead of stack
    let mut buf = Vec::with_capacity(8192);
    let mut written = 0;
    loop {
        let len = match from.read(&mut buf) {
            Ok(0) => return Ok(written),
            Ok(len) => len,
            Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
            Err(e) => return Err(e),
        };
        to.write_all(&buf[..len])?;
        written += len as u64;
    }
}